Rubber bushes of different designs depending on their particular function are used at different points above all in vehicle construction. An essential field of use is the mounting of parts of the wheel suspension and of the suspension arms. The vehicle manufacturer requires, in general, a high radial stiffness with a simultaneously low torsion spring rate for the bush bearings used to mount the suspension arms. The bush bearings shall effectively damp forces introduced radially, but they shall make it possible for the suspension to be able to move easily up and down.
A good ratio of the radial stiffness to the torsion spring rate is achieved by the use of slotted bushes. Like other elastomeric bush bearings as well, such bushes comprise an essentially cylindrical inner part, an outer sleeve concentrically surrounding the inner part and an elastomeric bearing body, which is arranged between the inner part and the outer sleeve and is connected at least to the two parts by vulcanization. Depending on the embodiment, one or more intermediate parts or intermediate plates are optionally arranged between the inner part and the outer sleeve. In bush bearings that are designed as slotted bushes, the outer sleeve and the optionally present intermediate parts have at least one axially extending longitudinal slot. The slot advantageously leads to a reduction of the shrinkage stresses after the vulcanization of the bearing parts. The diameter of the outer sleeve is reduced in the course of a calibration operation following the vulcanization. The slot is at least extensively closed as a result and a prestress is applied to the elastomeric bearing body, as a result of which the radial stiffness of the bearing increases. A higher degree of calibration is possible now due to the slot. As a result, softer blends or elastomers with lower Shore hardness can be used for the bearing body to reduce the torsion spring rate, and the bearing body will nevertheless have a high static radial stiffness based on the high degree of calibration. The ratio of the static radial stiffness to the torsion spring rate is consequently advantageously increased. The greater the angle of the notch opening forming the slot, i.e., the width of the slot, the greater is the radial stiffness of the bearing that can be set in the course of the calibration. However, the value of this angle and consequently of the outer width of the slot are limited, because there is a risk that the rubber forming the elastomeric bearing body will stream out in case of an excessively great slot width.
A slotted bush of this class is described, for example, in DT 19 55 308.
An increase in the radial stiffness can be achieved, furthermore, by the already mentioned use of intermediate parts, which are inserted into the bearing body between the inner part and the outer sleeve. This is also disclosed already by DT 19 55 308 cited above. To achieve the highest possible radial stiffness, a plurality of such intermediate parts are also rather frequently arranged concentrically with one another. However, a limit is set here by the space available at the site of installation of the bearing. Moreover, the use of a plurality of intermediate parts is difficult in terms of manufacturing technology and therefore also leads to higher manufacturing costs, besides to increased material costs. In addition, the risk of development of adhesion errors between the intermediate parts and the elastomer increases with increasing number of intermediate parts.
A bush bearing with a slot, in which a collar is formed at the axial ends of the outer sleeve to increase the axial stiffness of the bush bearing, is known from DT 15 25 131. However, compared with this, the slotted bushes known from the state of the art so far have only a comparatively low axial stiffness for manufacturing technological reasons. As a result, there is a risk that elastomeric slotted bushes used to mount the suspension arm will migrate axially outwardly when higher axial loads occur. It is desirable from this point of view that slotted bushes also have the highest possible axial stiffness. The possibility of penetration of dirt from the axial direction also represents a problem in the slotted bushes known from the state of the art.